The research on pore structure of tight reservoirs is of great significance for the exploration and development of tight oil and gas, and it is also a hotspot in the research on tight reservoirs. Taking the tight conglomerates of the Triassic Baikouquan Formation in the Junggar basin and tight sandstones of the Triassic Yanchang Formation in the Ordos basin as examples, the pore structure characteristics and comparisons of tight conglomerates and tight sandstones are studied qualitatively and quantitatively, and the differences of genetic mechanism between them are further explored using two- dimensional large area backscatter scanning electron microscopy (maps), high- pressure mercury intrusion porosimetry (HMIP), micro CT and focused ion beam scanning electron microscopy (FIB- SEM). Results show that the physical properties of tight conglomerate in the Baikouquan Formation are better than those of tight sandstone in the Yanchang Formation, and the average porosity and permeability of the former is 9. 29% and 1. 65×10-3 μm2, while that of the latter is 8. 85% and 0. 39×10-3 μm2. The pore throat distribution of tight conglomerates in the Baikouquan Formation and tight sandstone in the Yanchang Formation is characterized by multi- scale continuous distribution. The pore structure of tight conglomerates in the Baikouquan Formation is characterized by pore throat radius mainly in the range of 0~200 nm and 2~10 μm, average connectivity of 60. 63% and average pore- throat coordination number of 3. 0446. The pore structure of tight sandstones in the Yanchang Formation is characterized by pore throat radius mainly in the range of 0~4 μm, average connectivity of 73. 60% and average pore- throat coordination number of 2. 7832. Compared with the tight sandstones of the Yanchang Formation, the tight conglomerates of the Baikouquan Formation have larger pore throat size, poor pore throat sorting, poor pore connectivity and more complex pore structure. Differential sedimentation and diagenesis are the main reasons for the pore structure differences between tight conglomerates of the Baikouquan Formation and tight sandstones of the Yanchang Formation.